New records of mosquito species in the provinces of Chaco and Formosa, Argentina.

Seven mosquito species are recorded for the 1st time for northeastern Argentina: Culex (Melanoconion) albinensis, Cx. (Mel.) elevator, Cx. (Mel.) intrincatus, and Cx. (Mel.) serratimarge for Formosa Province, and Sabethes (Peytonulus) undosus, Sa. (Sabethinus) melanoninphe, and Toxorhynchites (Lynchiella) theobaldi for Chaco Province. The geographical distribution of these species is extended to northeastern Argentina, and the number of species increases to 97 and 75 for the provinces of Chaco and Formosa, respectively.